牛客网剑指offer刷题Java版-4重建二叉树

重建二叉树

题目描述
输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
import java.util.Arrays;
public class Solution {
    public TreeNode reConstructBinaryTree(int [] pre,int [] in) {
        if(pre.length==0||in.length==0){
            return null;
        }
        else{
            TreeNode tree=new TreeNode(pre[0]);
            for(int i=0;i<in.length;i++)
            {
                if(pre[0]==in[i]){
                    tree.left=reConstructBinaryTree(Arrays.copyOfRange(pre,1,i+1 ),Arrays.copyOfRange(in, 0, i));
                    tree.right=reConstructBinaryTree(Arrays.copyOfRange(pre,i+1,pre.length),Arrays.copyOfRange(in, i+1,in.length));
                    break;
                }
            }
            return tree;
        }
    }
}